import pygame
import sys

pygame.init()
screen = pygame.display.set_mode((400, 300))
background = pygame.Surface((400, 300))

surface = pygame.Surface((10, 10))
detail = pygame.Surface((4, 4))
surface.fill((0,255,0))
detail.fill((255, 0, 0))

detailpos = [175, 125]
POS = [172, 122]

while True:
    events = pygame.event.get()
    for event in events:
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_RIGHT:
                POS[0] += 20
                detailpos[0] += 20
            if event.key == pygame.K_LEFT:
                POS[0] = POS[0] - 20
                detailpos[0] = detailpos[0] - 20
            if event.key == pygame.K_DOWN:
                POS[1] += 20
                detailpos[1] += 20
            if event.key == pygame.K_UP:
                POS[1] = POS[1] - 20
                detailpos[1] = detailpos[1] - 20
    screen.blit(background, (0, 0))
    screen.blit(surface, POS)

    if POS > [400] or POS < [0]:
        pygame.quit()
        sys.exit()


    
    screen.blit(detail, detailpos)
    pygame.display.update()